Polymers, resist compositions and patterning process

ABSTRACT

A polymer comprising units of formulas (1) and (2) and having a Mw of 1,000-500,000 is provided. R 1  is H, CH 3  or CH 2 CO 2 R 3 , R 2  is H, CH 3  or CO 2 R 3 , R 3  is alkyl, R 4  is halogen or acyloxy, alkoxycarbonyloxy or alkylsulfonyloxy group which may be substituted with halogen, R 5  is H or alkyl, R 6  is an acid labile group, Z is a single bond or a divalent hydrocarbon group, k is 0 or 1, and W is —O— or —(NR)— wherein R is H or alkyl. A resist composition comprising the polymer as a base resin is sensitive to high-energy radiation, has excellent sensitivity, resolution, and etching resistance, and lends itself to micropatterning with electron beams or deep-UV rays.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to (i) a polymer comprising unitshaving an electron attractive group at a specific position, (ii) aresist composition comprising the polymer, having improved transparencyand hence, a high resolution, and in particular, suitable asmicropatterning material for VLSI fabrication, and (iii) a patterningprocess using the resist composition.

[0003] 2. Prior Art

[0004] While a number of recent efforts are being made to achieve afiner pattern rule in the drive for higher integration and operatingspeeds in LSI devices, deep-ultraviolet lithography is thought to holdparticular promise as the next generation in microfabricationtechnology. In particular, photolithography using a KrF or ArF excimerlaser as the light source is strongly desired to reach the practicallevel as the micropatterning technique capable of achieving a featuresize of 0.3 μm or less.

[0005] The resist materials for use in photolithography using light ofan excimer laser, especially ArF excimer laser having a wavelength of193 nm, are, of course, required to have a high transmittance to lightof that wavelength. In addition, they are required to have an etchingresistance sufficient to allow for film thickness reduction, a highsensitivity sufficient to eliminate any extra burden on the expensiveoptical material, and especially, a high resolution sufficient to form aprecise micropattern. To meet these requirements, it is crucial todevelop a base resin having a high transparency, robustness andreactivity. None of the currently available polymers satisfy all ofthese requirements. Practically acceptable resist materials are not yetavailable.

[0006] Known high transparency resins include copolymers of acrylic ormethacrylic acid derivatives and polymers containing in the backbone analicyclic compound derived from a norbornene derivative. All theseresins are unsatisfactory. For example, copolymers of acrylic ormethacrylic acid derivatives are relatively easy to increase reactivityin that highly reactive monomers can be introduced and acid labile unitscan be increased as desired, but difficult to increase robustnessbecause of their backbone structure. On the other hand, the polymerscontaining an alicyclic compound in the backbone have robustness withinthe acceptable range, but are less reactive with acid thanpoly(meth)acrylate because of their backbone structure, and difficult toincrease reactivity because of the low freedom of polymerization.Additionally, since these resins are less transparent thanpoly(meth)acrylates, they tend to further exaggerate the shortage ofreactivity. Therefore, for both poly(meth)acrylates and polymerscontaining an alicyclic compound in the backbone, some resistcompositions which are formulated using these polymers as the base resinfail to withstand etching although they have satisfactory sensitivityand resolution. Some other resist compositions are highly resistant toetching, but have low sensitivity and low resolution below thepractically acceptable level.

SUMMARY OF THE INVENTION

[0007] An object of the invention is to provide (i) a polymer featuringboth robustness and transparency, (ii) a resist composition comprisingthe polymer, having a significantly higher sensitivity, resolution, andetching resistance than prior art resist compositions, and (iii) apatterning process using the resist composition.

[0008] It has been found that a polymer comprising units of formulas (1)and (2) to be defined below and having a weight average molecular weightof 1,000 to 500,000 has very high transparency owing to the inclusion ofan electron attractive group at a specific position, and that a resistcomposition comprising the polymer has a significantly high sensitivity,resolution, and etching resistance and is thus quite useful in precisemicropatterning.

[0009] In a first aspect, the invention provides a polymer comprisingunits of the following general formula (1) and units of the followinggeneral formula (2) and having a weight average molecular weight of1,000 to 500,000.

[0010] Herein R¹ is hydrogen, methyl or CH₂CO₂R³, R² is hydrogen, methylor CO₂R³, R³ is a straight, branched or cyclic alkyl group of 1 to 15carbon atoms, R⁴ is a halogen atom or an acyloxy, alkoxycarbonyloxy oralkylsulfonyloxy group of 1 to 15 carbon atoms in which some or all ofthe hydrogen atoms on the constituent carbon atoms may be substitutedwith halogen atoms, R⁵ is hydrogen or a straight, branched or cyclicalkyl group of 1 to 10 carbon atoms, R⁶ is an acid labile group, Z is asingle bond or a divalent straight, branched or cyclic hydrocarbon groupof 1 to 10 carbon atoms, and k is 0 or 1. W is —O— or —(NR)— wherein Ris hydrogen or a straight, branched or cyclic alkyl group of 1 to 15carbon atoms.

[0011] Typical of the units of formula (1) are units of the followinggeneral formula (3) or (4).

[0012] Herein R¹ to R⁵, Z, and k are as defined above. R⁷ to R¹⁰ areindependently selected from straight, branched or cyclic alkyl groups of1 to 8 carbon atoms and substituted or unsubstituted aryl groups of 6 to20 carbon atoms, and Y is a divalent hydrocarbon group of 4 to 15 carbonatoms which may contain a hetero atom and which forms a ring with thecarbon atom to which it is connected at opposite ends.

[0013] The polymer may further include units of at least one of thefollowing formulas (5) to (8).

[0014] Herein R¹, R² and k are as defined above. At least one of R¹¹ toR¹⁴ is a carboxyl or hydroxyl-containing monovalent hydrocarbon group of1 to 15 carbon atoms, and the remainders are independently hydrogen or astraight, branched or cyclic alkyl group of 1 to 15 carbon atoms, or R¹¹to R¹⁴, taken together, may form a ring, and when they form a ring, atleast one of R¹¹ to R¹⁴ is a carboxyl or hydroxyl-containing divalenthydrocarbon group of 1 to 15 carbon atoms, and the remainders areindependently a single bond or a straight, branched or cyclic alkylenegroup of 1 to 15 carbon atoms. At least one of R¹⁵ to R¹⁸ is amonovalent hydrocarbon group of 2 to 15 carbon atoms containing a —CO₂—partial structure, and the remainders are independently hydrogen or astraight, branched or cyclic alkyl group of 1 to 15 carbon atoms, or R¹⁵to R¹⁸, taken together, may form a ring, and when they form a ring, atleast one of R¹⁵ to R¹⁸ is a divalent hydrocarbon group of 1 to 15carbon atoms containing a —CO₂— partial structure, and the remaindersare independently a single bond or a straight, branched or cyclicalkylene group of 1 to 15 carbon atoms. R¹⁹ is a polycyclic hydrocarbongroup of 7 to 15 carbon atoms or an alkyl group containing such apolycyclic hydrocarbon group. R²⁰ is an acid labile group. X is —CH₂— or—O—.

[0015] In a second aspect, the invention provides a resist compositioncomprising the polymer defined above.

[0016] In a third aspect, the invention provides a process for forming aresist pattern comprising the steps of applying the resist compositiononto a substrate to form a coating; heat treating the coating and thenexposing it to high-energy radiation or electron beams through a photomask; and optionally heat treating the exposed coating and developing itwith a developer.

[0017] In the units of formula (1), an electron attractive group hasbeen introduced on the carbon atom adjoining the aliphatic ring thatconstitutes the backbone. The electron attractive group introducedalters the overall electron distribution and steric structure of thepolymer and as a consequence, remarkably improves transparency for thereason which is unknown, and especially at the wavelength of 193 nm, toan equivalent level to poly(meth)acrylate. Accordingly, a resistcomposition using the polymer as a base resin eliminates the drawbacksof forward tapered shape and short-dissolution as found in prior artresist compositions, without detracting from the etching resistance andother advantages of a polymer containing an alicyclic compound in thebackbone.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0018] The polymer or high molecular weight compound of the invention isdefined as comprising units of the following general formulas (1) and(2) and having a weight average molecular weight of 1,000 to 500,000.

[0019] In formula (1), k is equal to 0 or 1. Then formula (1) can berepresented by the following formulas (1-1) and (1-2).

[0020] Herein, R¹ is hydrogen, methyl or CH₂CO₂R³. R² is hydrogen,methyl or CO₂R³. R³ stands for straight, branched or cyclic alkyl groupsof 1 to 15 carbon atoms, such as, for example, methyl, ethyl, propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl,cyclopentyl, cyclohexyl, ethylcyclopentyl, butylcyclopentyl,ethylcyclohexyl, butylcyclohexyl, adamantyl, ethyladamantyl andbutyladamantyl. R⁴ stands for halogen atoms or acyloxy,alkoxycarbonyloxy or alkylsulfonyloxy groups of 1 to 15 carbon atoms inwhich some or all of the hydrogen atoms on the constituent carbon atomsmay be substituted with halogen atoms, such as, for example, fluorine,chlorine, bromine, formyloxy, acetoxy, ethylcarbonyloxy, pivaloyloxy,methoxycarbonyloxy, ethoxycarbonyloxy, tert-butoxycarbonyloxy,methanesulfonyloxy, ethanesulfonyloxy, n-butanesulfonyloxy,trifluoroacetoxy, trichloroacetoxy, and 2,2,2-trifluoroethylcarbonyloxy.R⁵ stands for hydrogen or straight, branched or cyclic alkyl groups of 1to 10 carbon atoms, such as, for example, methyl, ethyl, propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl,cyclopentyl, cyclohexyl, cyclopentylethyl, cyclopentylbutyl,cyclohexylethyl and cyclohexylbutyl. R⁶ is an acid labile group. Z is asingle bond or a divalent straight, branched or cyclic hydrocarbon groupof 1 to 10 carbon atoms, such as methylene, ethane-1,1-diyl,ethane-1,2-diyl, propane-1,1-diyl, propane-1,2-diyl, propane-1,3-diyl,and cyclohexane-1,4-diyl.

[0021] W is —O— or —(NR)— wherein R is hydrogen or a straight, branchedor cyclic alkyl group of 1 to 15 carbon atoms, examples of which are thesame as exemplified for R³.

[0022] Exemplary acid labile groups represented by R⁶ are the same aswill be exemplified for R²⁰ although acid labile groups of the followingformulas are preferred.

[0023] Accordingly, units of the following general formula (3) or (4)are preferred among the units of formula (1).

[0024] Herein R¹ to R⁵, Z, and k are as defined above. R⁷ to R¹⁰ areindependently selected from straight, branched or cyclic alkyl groups of1 to 8 carbon atoms and substituted or unsubstituted aryl groups of 6 to20 carbon atoms. Examples of the straight, branched or cyclic alkylgroups include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl,tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl, cyclohexyl,cyclopentylmethyl, cyclopentyl-ethyl, cyclohexylmethyl, andcyclohexylethyl. Examples of the optionally substituted aryl groupinclude phenyl, methylphenyl, naphthyl, anthryl, phenanthryl andpyrenyl. Y is a divalent hydrocarbon group of 4 to 15 carbon atoms whichmay contain a hetero atom and which forms a ring with the carbon atom towhich it is connected at opposite ends. Examples of the rings that Yforms include cyclopentane, cyclopentene, cyclohexane, cyclohexene,bicyclo[2.2.1]heptane, bicyclo[4.4.0]decane,tricyclo[5.2.1.0^(2,6)]decane,tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodecane, and adamantane.

[0025] Illustrative, non-limiting, examples of the units of formula (1)and the units of formula (3) or (4) are given below.

[0026] The polymer of the invention may further comprise units of atleast one type selected from units of the following formulas (5) to (8).

[0027] In the above formulae, X is —CH₂— or —O—; and k is equal to 0or 1. Then formulae (5) to (8) may also be represented by the followingformulae (5-1) to (8-2).

[0028] Herein R¹, R², k and X are as defined above.

[0029] At least one of R¹¹ to R¹⁴ is a monovalent hydrocarbon group of 1to 15 carbon atoms (preferably straight, branched or cyclic alkyl) whichcontains a carboxyl or hydroxyl group, and the remaining R's areindependently hydrogen or a straight, branched or cyclic alkyl group of1 to 15 carbon atoms. Examples of the carboxyl or hydroxyl-bearingmonovalent hydrocarbon group of 1 to 15 carbon atoms include carboxy,carboxymethyl, carboxyethyl, carboxybutyl, hydroxymethyl, hydroxyethyl,hydroxybutyl, 2-carboxyethoxycarbonyl, 4-carboxybutoxycarbonyl,2-hydroxyethoxycarbonyl, 4-hydroxybutoxycarbonyl,carboxycyclopentyloxycarbonyl, carboxycyclohexyloxycarbonyl,carboxynorbornyloxycarbonyl, carboxyadamantyloxycarbonyl,hydroxycyclopentyloxycarbonyl, hydroxycyclohexyloxycarbonyl,hydroxynorbornyloxycarbonyl, and hydroxyadamantyloxycarbonyl. Examplesof the straight, branched or cyclic alkyl group of 1 to 15 carbon atomsare the same as exemplified for R³. R¹¹ to R¹⁴, taken together, may forma ring, and in that event, at least one of R¹¹ to R¹⁴ is a divalenthydrocarbon group of 1 to 15 carbon atoms (preferably straight, branchedor cyclic alkylene) having a carboxyl or hydroxyl group, while theremaining R's are independently single bonds or straight, branched orcyclic alkylene groups of 1 to 15 carbon atoms. Examples of the carboxylor hydroxyl-bearing divalent hydrocarbon group of 1 to 15 carbon atomsinclude the groups exemplified as the carboxyl or hydroxyl-bearingmonovalent hydrocarbon group, with one hydrogen atom eliminatedtherefrom. Examples of the straight, branched or cyclic alkylene groupsof 1 to 15 carbon atoms include the groups exemplified for R³, with onehydrogen atom eliminated therefrom.

[0030] At least one of R¹⁵ to R¹⁸ is a monovalent hydrocarbon group of 2to 15 carbon atoms containing a —CO₂— partial structure, while theremaining R's are independently hydrogen or straight, branched or cyclicalkyl groups of 1 to 15 carbon atoms. Examples of the monovalenthydrocarbon group of 2 to 15 carbon atoms containing a —CO₂— partialstructure include 2-oxooxolan-3-yloxycarbonyl,4,4-dimethyl-2-oxooxolan-3-yloxycarbonyl,4-methyl-2-oxooxan-4-yloxycarbonyl,2-oxo-1,3-dioxolan-4-ylmethyloxycarbonyl, and5-methyl-2-oxooxolan-5-yloxycarbonyl. Examples of the straight, branchedor cyclic alkyl groups of 1 to 15 carbon atoms are the same asexemplified for R³. R¹⁵ to R¹⁸, taken together, may form a ring, and inthat event, at least one of R¹⁵ to R¹⁸ is a divalent hydrocarbon groupof 1 to 15 carbon atoms containing a —CO₂— partial structure, while theremaining R's are independently single bonds or straight, branched orcyclic alkylene groups of 1 to 15 carbon atoms. Examples of the divalenthydrocarbon group of 1 to 15 carbon atoms containing a —CO₂— partialstructure include 1-oxo-2-oxapropane-1,3-diyl,1,3-dioxo-2-oxapropane-1,3-diyl, 1-oxo-2-oxabutane-1,4-diyl, and1,3-dioxo-2-oxabutane-1,4-diyl, as well as the groups exemplified as themonovalent hydrocarbon group containing a —CO₂— partial structure, withone hydrogen atom eliminated therefrom. Examples of the straight,branched or cyclic alkylene groups of 1 to 15 carbon atoms include thegroups exemplified for R³, with one hydrogen atom eliminated therefrom.

[0031] R¹⁹ is a polycyclic hydrocarbon group having 7 to 15 carbon atomsor an alkyl group containing a polycyclic hydrocarbon group, forexample, norbornyl, bicyclo[3.3.1]nonyl, tricyclo[5.2.1.0^(2,6)]decyl,adamantyl, ethyladamantyl, butyladamantyl, norbornylmethyl, andadamantylmethyl.

[0032] R²⁰ is an acid labile group. The acid labile groups representedby R²⁰ may be selected from a variety of such groups. Examples of theacid labile group are groups of the following general formulae (L1) to(L4), tertiary alkyl groups of 4 to 20 carbon atoms, preferably 4 to 15carbon atoms, trialkylsilyl groups in which each alkyl moiety has 1 to 6carbon atoms, and oxoalkyl groups of 4 to 20 carbon atoms.

[0033] In these formulas and throughout the specification, the brokenline denotes a valence bond.

[0034] R^(L01) and R^(L02) are hydrogen or straight, branched or cyclicalkyl groups of 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms.Exemplary alkyl groups include methyl, ethyl, propyl, isopropyl,n-butyl, sec-butyl, tert-butyl, cyclopentyl, cyclohexyl, 2-ethylhexyl,and n-octyl. R^(L03) is a monovalent hydrocarbon group of 1 to 18 carbonatoms, preferably 1 to 10 carbon atoms, which may contain a hetero atomsuch as oxygen, examples of which include unsubstituted straight,branched or cyclic alkyl groups and straight, branched or cyclic alkylgroups in which some hydrogen atoms are replaced by hydroxyl, alkoxy,oxo, amino, alkylamino or the like. Illustrative examples are thesubstituted alkyl groups shown below.

[0035] A pair of R^(L01) and R^(L02), R^(L01) and R^(L03), or R^(L02)and R^(L03) may form a ring. Each of R^(L01), R^(L02) and R^(L03) is astraight or branched alkylene group of 1 to 18 carbon atoms, preferably1 to 10 carbon atoms when they form a ring.

[0036] R^(L04) is a tertiary alkyl group of 4 to 20 carbon atoms,preferably 4 to 15 carbon atoms, a trialkylsilyl group in which eachalkyl moiety has 1 to 6 carbon atoms, an oxoalkyl group of 4 to 20carbon atoms, or a group of formula (L1). Exemplary tertiary alkylgroups are tert-butyl, tert-amyl, 1,1-diethylpropyl, 1-ethylcyclopentyl,1-butylcyclopentyl, 1-ethylcyclohexyl, 1-butylcyclohexyl,1-ethyl-2-cyclopentenyl, 1-ethyl-2-cyclohexenyl, and2-methyl-2-adamantyl. Exemplary trialkylsilyl groups are trimethylsilyl,triethylsilyl, and dimethyl-tert-butylsilyl. Exemplary oxoalkyl groupsare 3-oxocyclohexyl, 4-methyl-2-oxooxan-4-yl, and5-methyl-5-oxooxolan-4-yl. Letter y is an integer of 0 to 6.

[0037] R^(L05) is a straight or branched alkyl group of 1 to 8 carbonatoms or a substituted or unsubstituted aryl group of 6 to 20 carbonatoms. Examples of the straight, branched or cyclic alkyl group includemethyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,tert-amyl, n-pentyl and n-hexyl. Exemplary aryl groups are phenyl,methylphenyl, naphthyl, anthryl, phenanthryl, and pyrenyl. Letter m isequal to 0 or 1, n is equal to 0, 1, 2 or 3, and 2m+n is equal to 2 or3.

[0038] R^(L06) is a straight, branched or cyclic alkyl group of 1 to 8carbon atoms or a substituted or unsubstituted aryl group of 6 to 20carbon atoms. Examples of these groups are the same as exemplified forR^(L05).

[0039] R^(L07) to R^(L16) independently represent hydrogen or monovalenthydrocarbon groups of 1 to 15 carbon atoms which may contain a heteroatom. Exemplary hydrocarbon groups are straight, branched or cyclicalkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl,sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, n-octyl, n-nonyl,n-decyl, cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl,cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl and cyclohexylbutyl,and substituted ones of these groups in which some hydrogen atoms arereplaced by hydroxyl, alkoxy, carboxy, alkoxycarbonyl, oxo, amino,alkylamino, cyano, mercapto, alkylthio, sulfo or other groups.Alternatively, R^(L07) to R^(L16), taken together, form a ring (forexample, a pair of R^(L07) and R^(L08), R^(L07) and R^(L09), R^(L08) andR^(L10), R^(L09) and R^(L10), R^(L11) and R^(L12), R^(L13) and R^(L14),or a similar pair form a ring). Each of R^(L07) to R^(L16) represents adivalent C₁-C₁₅ hydrocarbon group which may contain a hetero atom, whenthey form a ring, examples of which are the ones exemplified above forthe monovalent hydrocarbon groups, with one hydrogen atom beingeliminated. Two of R^(L07) to R^(L16) which are attached to adjoiningcarbon atoms (for example, a pair of R^(L07) and R^(L09), R^(L09) andR^(L15), R^(L13) and R^(L15), or a similar pair) may bond togetherdirectly to form a double bond.

[0040] Of the acid labile groups of formula (L1), the straight andbranched ones are exemplified by the following groups.

[0041] Of the acid labile groups of formula (L1), the cyclic ones are,for example, tetrahydrofuran-2-yl, 2-methyltetrahydrofuran-2-yl,tetrahydropyran-2-yl, and 2-methyltetrahydropyran-2-yl.

[0042] Examples of the acid labile groups of formula (L2) includetert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-amyloxycarbonyl,tert-amyloxycarbonylmethyl, 1,1-diethylpropyloxycarbonyl,1,1-diethylpropyloxycarbonylmethyl, 1-ethylcyclopentyloxycarbonyl,1-ethylcyclopentyloxycarbonylmethyl, 1-ethyl-2-cyclopentenyloxycarbonyl,1-ethyl-2-cyclopentenyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl,2-tetrahydropyranyloxycarbonylmethyl, and2-tetrahydrofuranyloxycarbonylmethyl groups.

[0043] Examples of the acid labile groups of formula (L3) include1-methylcyclopentyl, 1-ethylcyclopentyl, 1-n-propylcyclopentyl,1-isopropylcyclopentyl, 1-n-butyl-cyclopentyl, 1-sec-butylcyclopentyl,1-methylcyclohexyl, 1-ethylcyclohexyl, 3-methyl-1-cyclopenten-3-yl,3-ethyl-1-cyclopenten-3-yl, 3-methyl-1-cyclohexen-3-yl, and3-ethyl-1-cyclohexen-3-yl groups.

[0044] The acid labile groups of formula (L4) are exemplified by thefollowing groups.

[0045] Examples of the tertiary alkyl groups, trialkylsilyl groups, andoxoalkyl groups included in the acid labile groups represented by R²⁰are as previously exemplified.

[0046] As the acid labile group represented by R²⁰, there may be usedone type or a combination of two or more types. The use of acid labilegroups of different types allows for fine adjustment of a patternprofile.

[0047] The polymer of the invention may be prepared by copolymerizing acompound of formula (1a) as a first monomer, a compound of formula (2a)as a second monomer and optionally, at least one member selected fromcompounds of formulas (5a) to (8a) as a third monomer (and subsequentmonomers).

[0048] Herein, R¹ to R²⁰, W, X, Y, Z and k are as defined above.

[0049] In addition to (i) the monomer of formula (1a), (ii) the monomerof formula (2a) and (iii) the optional monomer or monomers of formulas(5a) to (8a), the polymer of the invention may have copolymerizedtherewith (iv) another monomer having a carbon-to-carbon double bondother than (i) to (iii), if desired. Examples of the additional monomer(iv) include substituted acrylic acid esters such as methylmethacrylate, methyl crotonate, dimethyl maleate, and dimethylitaconate, unsaturated carboxylic acids such as maleic acid, fumaricacid and itaconic acid, substituted or unsubstituted norbornenes such asnorbornene and methyl norbornene-5-carboxylate, and unsaturated acidanhydrides such as itaconic anhydride.

[0050] Copolymerization reaction is effected by mixing the monomers (i)to (iv) in a suitable proportion which is determined by taking intoaccount the reactivity of the respective monomers, or dissolving themonomers in a solvent if desired, adding a suitable polymerizationinitiator or catalyst, and holding the reaction mixture at a suitabletemperature for a suitable time. Copolymerization reaction may beeffected in various modes although radical polymerization reaction ispreferred.

[0051] For radical polymerization, preferred reaction conditions include(a) a solvent selected from among hydrocarbons such as benzene, etherssuch as tetrahydrofuran, alcohols such as ethanol, and ketones such asmethyl isobutyl ketone, (b) a polymerization initiator selected from azocompounds such as 2,2′-azobisisobutyronitrile and peroxides such asbenzoyl peroxide and lauroyl peroxide, (c) a temperature of about 0° C.to about 100° C., and (d) a time of about ½ hour to about 48 hours.Reaction conditions outside the described range may be employed ifdesired.

[0052] By properly adjusting the proportion of the respective monomersused in the copolymerization reaction, the polymer can be tailored sothat it may exert the preferred performance when blended in resistcompositions.

[0053] The polymers of the invention may contain

[0054] (I) more than 0 mol % to 50 mol %, preferably 20 to 50 mol %,more preferably 30 to 50 mol % of units of formula (1) originating fromthe monomer of formula (1a),

[0055] (II) more than 0 mol % to 50 mol %, preferably 20 to 50 mol %,more preferably 30 to 50 mol % of units of formula (2) originating fromthe monomer of formula (2a), and optionally,

[0056] (III) 0 mol % to 50 mol %, preferably 0 to 30 mol %, morepreferably 0 to 20 mol % of units of one or more types of formulae (5)to (8) originating from the monomers of formulae (5a) to (8a), andfurther optionally,

[0057] (IV) 0 to 50 mol %, preferably 0 to 30 mol %, more preferably 0to 20 mol % of units of one or more types originating from theadditional monomers (iv). It is noted that compositions outside theabove range are not excluded from the invention.

[0058] The inventive polymers comprising units of formulas (1) and (2)have a weight average molecular weight of 1,000 to 500,000, preferably3,000 to 100,000. Outside the range, the etching resistance may becomeextremely low and the resolution may become low because a substantialdifference in rate of dissolution before and after exposure is lost.

[0059] Resist Composition

[0060] The polymer of the invention is useful as the base polymer of aresist composition, and the other aspect of the invention provides aresist composition comprising the polymer. Preferably, the resistcomposition is defined as comprising the polymer, a photoacid generator,and an organic solvent.

[0061] Photoacid Generator

[0062] The photoacid generator is a compound capable of generating anacid upon exposure to high energy radiation or electron beams andincludes the following:

[0063] (i) onium salts of the formula (P1a-1), (P1a-2) or (P1b),

[0064] (ii) diazomethane derivatives of the formula (P2),

[0065] (iii) glyoxime derivatives of the formula (P3),

[0066] (iv) bissulfone derivatives of the formula (P4),

[0067] (v) sulfonic acid esters of N-hydroxyimide compounds of theformula (P5),

[0068] (vi) β-ketosulfonic acid derivatives,

[0069] (vii) disulfone derivatives,

[0070] (viii) nitrobenzylsulfonate derivatives, and

[0071] (ix) sulfonate derivatives.

[0072] These photoacid generators are described in detail.

[0073] (i) Onium Salts of Formula (P1a-1), (P1a-2) or (P1b):

[0074] Herein, R^(101a), R^(101b), and R^(101c) independently representstraight, branched or cyclic alkyl, alkenyl, oxoalkyl or oxoalkenylgroups of 1 to 12 carbon atoms, aryl groups of 6 to 20 carbon atoms, oraralkyl or aryloxoalkyl groups of 7 to 12 carbon atoms, wherein some orall of the hydrogen atoms may be replaced by alkoxy or other groups.Also, R^(101b) and R^(101c), taken together, may form a ring. R^(101b)and R^(101c) each are alkylene groups of 1 to 6 carbon atoms when theyform a ring. K⁻ is a non-nucleophilic counter ion.

[0075] R^(101a), R^(101b), and R^(101c) may be the same or different andare illustrated below. Exemplary alkyl groups include methyl, ethyl,propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl,heptyl, octyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclopropylmethyl,4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl.Exemplary alkenyl groups include vinyl, allyl, propenyl, butenyl,hexenyl, and cyclohexenyl. Exemplary oxoalkyl groups include2-oxocyclopentyl and 2-oxocyclohexyl as well as 2-oxopropyl,2-cyclopentyl-2-oxoethyl, 2-cyclohexyl-2-oxoethyl, and2-(4-methylcyclohexyl)-2-oxoethyl. Exemplary aryl groups include phenyland naphthyl; alkoxyphenyl groups such as p-methoxyphenyl,m-methoxyphenyl, o-methoxyphenyl, ethoxyphenyl, p-tert-butoxyphenyl, andm-tert-butoxyphenyl; alkylphenyl groups such as 2-methylphenyl,3-methylphenyl, 4-methylphenyl, ethylphenyl, 4-tert-butylphenyl,4-butylphenyl, and dimethylphenyl; alkylnaphthyl groups such asmethylnaphthyl and ethylnaphthyl; alkoxynaphthyl groups such asmethoxynaphthyl and ethoxynaphthyl; dialkylnaphthyl groups such asdimethylnaphthyl and diethylnaphthyl; and dialkoxynaphthyl groups suchas dimethoxynaphthyl and diethoxynaphthyl. Exemplary aralkyl groupsinclude benzyl, phenylethyl, and phenethyl. Exemplary aryloxoalkylgroups are 2-aryl-2-oxoethyl groups such as 2-phenyl-2-oxoethyl,2-(1-naphthyl)-2-oxoethyl, and 2-(2-naphthyl)-2-oxoethyl. Examples ofthe non-nucleophilic counter ion represented by K⁻ include halide ionssuch as chloride and bromide ions, fluoroalkylsulfonate ions such astriflate, 1,1,1-trifluoroethanesulfonate, and nonafluorobutanesulfonate,arylsulfonate ions such as tosylate, benzenesulfonate,4-fluorobenzenesulfonate, and 1,2,3,4,5-pentafluorobenzenesulfonate, andalkylsulfonate ions such as mesylate and butanesulfonate.

[0076] Herein, R^(102a) and R^(102b) independently represent straight,branched or cyclic alkyl groups of 1 to 8 carbon atoms. R¹⁰³ representsa straight, branched or cyclic alkylene groups of 1 to 10 carbon atoms.R^(104a) and R^(104b) independently represent 2-oxoalkyl groups of 3 to7 carbon atoms. K⁻ is a non-nucleophilic counter ion.

[0077] Illustrative of the groups represented by R^(102a) and R^(102b)are methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,pentyl, hexyl, heptyl, octyl, cyclopentyl, cyclohexyl,cyclopropylmethyl, 4-methylcyclohexyl, and cyclohexylmethyl.Illustrative of the groups represented by R¹⁰³ are methylene, ethylene,propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene,1,4-cyclohexylene, 1,2-cyclohexylene, 1,3-cyclopentylene,1,4-cyclooctylene, and 1,4-cyclohexanedimethylene. Illustrative of thegroups represented by R^(104a) and R^(104b) are 2-oxopropyl,2-oxocyclopentyl, 2-oxocyclohexyl, and 2-oxocycloheptyl. Illustrativeexamples of the counter ion represented by K⁻ are the same asexemplified for formulae (P1a-1) and (P1a-2).

[0078] (ii) Diazomethane Derivatives of Formula (P2)

[0079] Herein, R¹⁰⁵ and R¹⁰⁶ independently represent straight, branchedor cyclic alkyl or halogenated alkyl groups of 1 to 12 carbon atoms,aryl or halogenated aryl groups of 6 to 20 carbon atoms, or aralkylgroups of 7 to 12 carbon atoms.

[0080] Of the groups represented by R¹⁰⁵ and R¹⁰⁶, exemplary alkylgroups include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl,tert-butyl, pentyl, hexyl, heptyl, octyl, amyl, cyclopentyl, cyclohexyl,cycloheptyl, norbornyl, and adamantyl. Exemplary halogenated alkylgroups include trifluoromethyl, 1,1,1-trifluoroethyl,1,1,1-trichloroethyl, and nonafluorobutyl. Exemplary aryl groups includephenyl; alkoxyphenyl groups such as p-methoxyphenyl, m-methoxyphenyl,o-methoxyphenyl, ethoxyphenyl, p-tert-butoxyphenyl, andm-tert-butoxyphenyl; and alkylphenyl groups such as 2-methylphenyl,3-methylphenyl, 4-methylphenyl, ethylphenyl, 4-tert-butylphenyl,4-butylphenyl, and dimethylphenyl. Exemplary halogenated aryl groupsinclude fluorophenyl, chlorophenyl, and 1,2,3,4,5-pentafluorophenyl.Exemplary aralkyl groups include benzyl and phenethyl.

[0081] (iii) Glyoxime Derivatives of Formula (P3)

[0082] Herein, R¹⁰⁷, R¹⁰⁸, and R¹⁰⁹ independently represent straight,branched or cyclic alkyl or halogenated alkyl groups of 1 to 12 carbonatoms, aryl or halogenated aryl groups of 6 to 20 carbon atoms, oraralkyl groups of 7 to 12 carbon atoms. Also, R¹⁰⁸ and R¹⁰⁹, takentogether, may form a ring. R¹⁰⁸ and R¹⁰⁹ each are straight or branchedalkylene groups of 1 to 6 carbon atoms when they form a ring.

[0083] Illustrative examples of the alkyl, halogenated alkyl, aryl,halogenated aryl, and aralkyl groups represented by R¹⁰⁷, R¹⁰⁸, and R¹⁰⁹are the same as exemplified for R¹⁰⁵ and R¹⁰⁶. Examples of the alkylenegroups represented by R¹⁰⁸ and R¹⁰⁹ include methylene, ethylene,propylene, butylene, and hexylene.

[0084] (iv) Bissulfone Derivatives of Formula (P4)

[0085] Herein, R^(101a) and R^(101b) are as defined above.

[0086] (v) Sulfonic Acid Esters of N-hydroxyimide Compounds of Formula(P5)

[0087] Herein, R¹¹⁰ is an arylene group of 6 to 10 carbon atoms,alkylene group of 1 to 6 carbon atoms, or alkenylene group of 2 to 6carbon atoms wherein some or all of the hydrogen atoms may be replacedby straight or branched alkyl or alkoxy groups of 1 to 4 carbon atoms,nitro, acetyl, or phenyl groups. R¹¹¹ is a straight, branched or cyclicalkyl group of 1 to 8 carbon atoms, alkenyl, alkoxyalkyl, phenyl ornaphthyl group wherein some or all of the hydrogen atoms may be replacedby alkyl or alkoxy groups of 1 to 4 carbon atoms, phenyl groups (whichmay have substituted thereon an alkyl or alkoxy of 1 to 4 carbon atoms,nitro, or acetyl group), hetero-aromatic groups of 3 to 5 carbon atoms,or chlorine or fluorine atoms.

[0088] Of the groups represented by R¹¹⁰, exemplary arylene groupsinclude 1,2-phenylene and 1,8-naphthylene; exemplary alkylene groupsinclude methylene, 1,2-ethylene, 1,3-propylene, 1,4-butylene,1-phenyl-1,2-ethylene, and norbornane-2,3-diyl; and exemplary alkenylenegroups include 1,2-vinylene, 1-phenyl-1,2-vinylene, and5-norbornene-2,3-diyl. Of the groups represented by R¹¹¹, exemplaryalkyl groups are as exemplified for R^(101a) and R^(101c); exemplaryalkenyl groups include vinyl, 1-propenyl, allyl, 1-butenyl, 3-butenyl,isoprenyl, 1-pentenyl, 3-pentenyl, 4-pentenyl, dimethylallyl, 1-hexenyl,3-hexenyl, 5-hexenyl, 1-heptenyl, 3-heptenyl, 6-heptenyl, and 7-octenyl;and exemplary alkoxyalkyl groups include methoxymethyl, ethoxymethyl,propoxymethyl, butoxymethyl, pentyloxymethyl, hexyloxymethyl,heptyloxymethyl, methoxyethyl, ethoxyethyl, propoxyethyl, butoxyethyl,pentyloxyethyl, hexyloxyethyl, methoxypropyl, ethoxypropyl,propoxypropyl, butoxypropyl, methoxybutyl, ethoxybutyl, propoxybutyl,methoxypentyl, ethoxypentyl, methoxyhexyl, and methoxyheptyl.

[0089] Of the substituents on these groups, the alkyl groups of 1 to 4carbon atoms include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyland tert-butyl; the alkoxy groups of 1 to 4 carbon atoms includemethoxy, ethoxy, propoxy, isopropoxy, n-butoxy, isobutoxy, andtert-butoxy; the phenyl groups which may have substituted thereon analkyl or alkoxy of 1 to 4 carbon atoms, nitro, or acetyl group includephenyl, tolyl, p-tert-butoxyphenyl, p-acetylphenyl and p-nitrophenyl;the hetero-aromatic groups of 3 to 5 carbon atoms include pyridyl andfuryl.

[0090] Illustrative examples of the photoacid generator include:

[0091] onium salts such as diphenyliodonium trifluoromethanesulfonate,(p-tert-butoxyphenyl)phenyliodonium trifluoromethanesulfonate,diphenyliodonium p-toluenesulfonate, (p-tert-butoxyphenyl)phenyliodoniump-toluenesulfonate, triphenylsulfonium trifluoromethanesulfonate,(p-tert-butoxyphenyl)diphenylsulfonium trifluoromethanesulfonate,bis(p-tert-butoxyphenyl)phenylsulfonium trifluoromethanesulfonate,tris(p-tert-butoxyphenyl)sulfonium trifluoromethanesulfonate,triphenylsulfonium p-toluenesulfonate,(p-tert-butoxyphenyl)diphenylsulfonium p-toluenesulfonate,bis(p-tert-butoxyphenyl)phenylsulfonium p-toluenesulfonate,tris(p-tert-butoxyphenyl)sulfonium p-toluenesulfonate,triphenylsulfonium nonafluorobutanesulfonate, triphenylsulfoniumbutanesulfonate, trimethylsulfonium trifluoromethanesulfonate,trimethylsulfonium p-toluenesulfonate,cyclohexylmethyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate,cyclohexylmethyl(2-oxocyclohexyl)sulfonium p-toluenesulfonate,dimethylphenylsulfonium trifluoromethanesulfonate,dimethylphenylsulfonium p-toluenesulfonate, dicyclohexylphenylsulfoniumtrifluoromethanesulfonate, dicyclohexylphenylsulfoniump-toluenesulfonate, trinaphthylsulfonium trifluoromethanesulfonate,cyclohexylmethyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate,(2-norbornyl)methyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate,ethylenebis[methyl(2-oxocyclopentyl)sulfoniumtrifluoromethanesulfonate], and1,2′-naphthylcarbonylmethyltetrahydrothiophenium triflate;

[0092] diazomethane derivatives such asbis(benzenesulfonyl)diazomethane, bis(p-toluenesulfonyl)diazomethane,bis(xylenesulfonyl)diazomethane, bis(cyclohexylsulfonyl)diazomethane,bis(cyclopentylsulfonyl)diazomethane, bis(n-butylsulfonyl)diazomethane,bis(isobutylsulfonyl)diazomethane, bis(sec-butylsulfonyl)diazomethane,bis(n-propylsulfonyl)diazomethane, bis(isopropylsulfonyl)diazomethane,bis(tert-butylsulfonyl)diazomethane, bis(n-amylsulfonyl)diazomethane,bis(isoamylsulfonyl)diazomethane, bis(sec-amylsulfonyl)diazomethane,bis(tert-amylsulfonyl)diazomethane,1-cyclohexylsulfonyl-1-(tert-butylsulfonyl)diazomethane,1-cyclohexylsulfonyl-1-(tert-amylsulfonyl)diazomethane, and1-tert-amylsulfonyl-1-(tert-butylsulfonyl)diazomethane;

[0093] glyoxime derivatives such asbis-o-(p-toluenesulfonyl)-α-dimethylglyoxime,bis-o-(p-toluenesulfonyl)-α-diphenylglyoxime,bis-o-(p-toluenesulfonyl)-α-dicyclohexylglyoxime,bis-o-(p-toluenesulfonyl)-2,3-pentanedioneglyoxime,bis-o-(p-toluenesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,bis-o-(n-butanesulfonyl)-α-dimethylglyoxime,bis-o-(n-butanesulfonyl)-α-diphenylglyoxime,bis-o-(n-butanesulfonyl)-α-dicyclohexylglyoxime,bis-o-(n-butanesulfonyl)-2,3-pentanedioneglyoxime,bis-o-(n-butanesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,bis-o-(methanesulfonyl)-α-dimethylglyoxime,bis-o-(trifluoroethanesulfonyl)-α-dimethylglyoxime,bis-o-(1,1,1-trifluorothanesulfonyl)-α-dimethylglyoxime,bis-o-(tert-butanesulfonyl)-α-dimethylglyoxime,bis-o-(perfluorooctanesulfonyl)-α-dimethylglyoxime,bis-o-(cyclohexanesulfonyl)-α-dimethylglyoxime,bis-o-(benzenesulfonyl)-(α-dimethylglyoxime,bis-o-(p-fluorobenzenesulfonyl)-α-dimethylglyoxime,bis-o-(p-tert-butylbenzenesulfonyl)-α-dimethylglyoxime,bis-o-(xylenesulfonyl)-α-dimethylglyoxime, andbis-o-(camphorsulfonyl)-α-dimethylglyoxime;

[0094] bissulfone derivatives such as bisnaphthylsulfonylmethane,bistrifluoromethylsulfonylmethane, bismethylsulfonylmethane,bisethylsulfonylmethane, bispropylsulfonylmethane,bisisopropylsulfonylmethane, bis-p-toluenesulfonylmethane, andbisbenzenesulfonylmethane;

[0095] β-ketosulfone derivatives such as2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane and2-isopropylcarbonyl-2-(p-toluenesulfonyl)propane;

[0096] disulfone derivatives such as diphenyl disulfone and dicyclohexyldisulfone;

[0097] nitrobenzyl sulfonate derivatives such as 2,6-dinitrobenzylp-toluenesulfonate and 2,4-dinitrobenzyl p-toluenesulfonate;

[0098] sulfonic acid ester derivatives such as1,2,3-tris-(methanesulfonyloxy)benzene,1,2,3-tris(trifluoromethanesulfonyloxy)benzene, and1,2,3-tris(p-toluenesulfonyloxy)benzene; and

[0099] sulfonic acid esters of N-hydroxyimides such asN-hydroxysuccinimide methanesulfonate, N-hydroxysuccinimidetrifluoromethanesulfonate, N-hydroxysuccinimide ethanesulfonate,N-hydroxysuccinimide 1-propanesulfonate, N-hydroxysuccinimide2-propanesulfonate, N-hydroxysuccinimide 1-pentanesulfonate,N-hydroxysuccinimide 1-octanesulfonate, N-hydroxysuccinimidep-toluenesulfonate, N-hydroxysuccinimide p-methoxybenzenesulfonate,N-hydroxysuccinimide 2-chloroethanesulfonate, N-hydroxysuccinimidebenzenesulfonate, N-hydroxysuccinimide 2,4,6-trimethylbenzenesulfonate,N-hydroxysuccinimide 1-naphthalenesulfonate, N-hydroxysuccinimide2-naphthalenesulfonate, N-hydroxy-2-phenylsuccinimide methanesulfonate,N-hydroxymaleimide methanesulfonate, N-hydroxymaleimide ethanesulfonate,N-hydroxy-2-phenylmaleimide methanesulfonate, N-hydroxyglutarimidemethanesulfonate, N-hydroxyglutarimide benzenesulfonate,N-hydroxyphthalimide methanesulfonate, N-hydroxyphthalimidebenzenesulfonate, N-hydroxyphthalimide trifluoromethanesulfonate,N-hydroxyphthalimide p-toluenesulfonate, N-hydroxynaphthalimidemethanesulfonate, N-hydroxynaphthalimide benzenesulfonate,N-hydroxy-5-norbornene-2,3-dicarboxyimide methanesulfonate,N-hydroxy-5-norbornene-2,3-dicarboxyimide trifluoromethanesulfonate, andN-hydroxy-5-norbornene-2,3-dicarboxyimide p-toluenesulfonate.

[0100] Preferred among these photoacid generators are onium salts suchas triphenylsulfonium trifluoromethanesulfonate,(p-tert-butoxyphenyl)diphenylsulfonium trifluoromethanesulfonate,tris(p-tert-butoxyphenyl)sulfonium trifluoromethanesulfonate,triphenylsulfonium p-toluenesulfonate,(p-tert-butoxyphenyl)diphenylsulfonium p-toluenesulfonate,tris(p-tert-butoxyphenyl)sulfonium p-toluenesulfonate,trinaphthylsulfonium trifluoromethanesulfonate,cyclohexylmethyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate,(2-norbornyl)methyl(2-oxocylohexyl)sulfonium trifluoromethanesulfonate,and 1,2′-naphthylcarbonylmethyltetrahydrothiophenium triflate;diazomethane derivatives such as bis(benzenesulfonyl)diazomethane,bis(p-toluenesulfonyl)diazomethane, bis(cyclohexylsulfonyl)diazomethane,bis(n-butylsulfonyl)diazomethane, bis(isobutylsulfonyl)diazomethane,bis(sec-butylsulfonyl)diazomethane, bis(n-propylsulfonyl)diazomethane,bis(isopropylsulfonyl)diazomethane, andbis(tert-butylsulfonyl)diazomethane; glyoxime derivatives such asbis-o-(p-toluenesulfonyl)-α-dimethylglyoxime andbis-o-(n-butanesulfonyl)-α-dimethylglyoxime; bissulfone derivatives suchas bisnaphthylsulfonylmethane; and sulfonic acid esters ofN-hydroxyimide compounds such as N-hydroxysuccinimide methanesulfonate,N-hydroxysuccinimide trifluoromethanesulfonate, N-hydroxysuccinimide1-propanesulfonate, N-hydroxysuccinimide 2-propanesulfonate,N-hydroxysuccinimide 1-pentanesulfonate, N-hydroxysuccinimidep-toluenesulfonate, N-hydroxynaphthalimide methanesulfonate, andN-hydroxynaphthalimide benzenesulfonate.

[0101] These photoacid generators may be used singly or in combinationsof two or more thereof. Onium salts are effective for improvingrectangularity, while diazomethane derivatives and glyoxime derivativesare effective for reducing standing waves. The combination of an oniumsalt with a diazomethane or a glyoxime derivative allows for fineadjustment of the profile.

[0102] The photoacid generator is added in an amount of 0.1 to 15 parts,and especially 0.5 to 8 parts by weight, per 100 parts by weight of thebase resin (all parts are by weight, hereinafter). Less than 0.1 part ofthe photoacid generator would provide a poor sensitivity whereas morethan 15 parts of the photoacid generator would adversely affecttransparency and resolution.

[0103] Organic Solvent

[0104] The organic solvent used herein may be any organic solvent inwhich the base resin, photoacid generator, and other components aresoluble. Illustrative, non-limiting, examples of the organic solventinclude ketones such as cyclohexanone and methyl-2-n-amylketone;alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol,1-methoxy-2-propanol, and 1-ethoxy-2-propanol; ethers such as propyleneglycol monomethyl ether, ethylene glycol monomethyl ether, propyleneglycol monoethyl ether, ethylene glycol monoethyl ether, propyleneglycol dimethyl ether, and diethylene glycol dimethyl ether; and esterssuch as propylene glycol monomethyl ether acetate, propylene glycolmonoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate,methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butylacetate, tert-butyl propionate, and propylene glycol mono-tert-butylether acetate. These solvents may be used alone or in combinations oftwo or more thereof. Of the above organic solvents, it is recommended touse diethylene glycol dimethyl ether and 1-ethoxy-2-propanol because thephotoacid generator serving as one of the resist components is mostsoluble therein, propylene glycol monomethyl ether acetate because it isa safe solvent, or a mixture thereof.

[0105] An appropriate amount of the organic solvent used is about 200 to1,000 parts, especially about 400 to 800 parts by weight per 100 partsby weight of the base resin.

[0106] Other Polymer

[0107] To the resist composition of the invention, another polymer otherthan the inventive polymer comprising units of formulas (1) and (2) mayalso be added. The other polymers that can be added to the resistcomposition are, for example, those polymers comprising units of thefollowing formula (R1) and/or (R2) and having a weight average molecularweight of about 1,000 to about 500,000, especially about 5,000 to about100,000 although the other polymers are not limited thereto.

[0108] Herein, R⁰⁰¹ is hydrogen, methyl or CH₂CO₂R⁰⁰³. R⁰⁰² is hydrogen,methyl or CO₂R⁰⁰³. R⁰⁰³ is a straight, branched or cyclic alkyl group of1 to 15 carbon atoms. R⁰⁰⁴ is hydrogen or a monovalent hydrocarbon groupof 1 to 15 carbon atoms having a carboxyl or hydroxyl group. At leastone of R⁰⁰⁵ to R⁰⁰⁸ represents a monovalent hydrocarbon group of 1 to 15carbon atoms having a carboxyl or hydroxyl group while the remaining R'sindependently represent hydrogen or a straight, branched or cyclic alkylgroup of 1 to 15 carbon atoms. Alternatively, R⁰⁰⁵ to R⁰⁰⁸, takentogether, may form a ring, and in that event, at least one of R⁰⁰⁵ toR⁰⁰⁸ is a divalent hydrocarbon group of 1 to 15 carbon atoms having acarboxyl or hydroxyl group, while the remaining R's are independentlysingle bonds or straight, branched or cyclic alkylene groups of 1 to 15carbon atoms. R⁰⁰⁹ is a monovalent hydrocarbon group of 3 to 15 carbonatoms containing a —CO₂— partial structure. At least one of R⁰¹⁰ to R⁰¹³is a monovalent hydrocarbon group of 2 to 15 carbon atoms containing a—CO₂— partial structure, while the remaining R's are independentlyhydrogen or straight, branched or cyclic alkyl groups of 1 to 15 carbonatoms. R⁰¹⁰ to R⁰¹³, taken together, may form a ring, and in that event,at least one of R⁰¹⁰ to R⁰¹³ is a divalent hydrocarbon group of 1 to 15carbon atoms containing a —CO₂— partial structure, while the remainingR's are independently single bonds or straight, branched or cyclicalkylene groups of 1 to 15 carbon atoms. R⁰¹⁴ is a polycyclichydrocarbon group having 7 to 15 carbon atoms or an alkyl groupcontaining a polycyclic hydrocarbon group. R⁰¹⁵ is an acid labile group.R⁰¹⁶ is hydrogen or methyl. R⁰¹⁷ is a straight, branched or cyclic alkylgroup of 1 to 8 carbon atoms. Letter k′ is equal to 0 or 1; a1′, a2′,a3′, b1′, b2′, b3′, c1′, c2′, c3′, d1′, d2′, d3′, and e′ are numbersfrom 0 to less than 1, satisfyinga1′+a2′+a3′+b1′+b2′+b3′+c1′+c2′+c3′+d1′+d2′+d3′+e′=1; f′, g′, h′, i′,and j′ are numbers from 0 to less than 1, satisfying f′+g′+h′+i′+j′=1.

[0109] Exemplary groups of these R's are as exemplified above for R¹ toR²⁰.

[0110] The inventive polymer (comprising units of formulas (1) and (2))and the other polymer are preferably blended in a weight ratio from10:90 to 90:10, more preferably from 20:80 to 80:20. If the blend ratioof the inventive polymer is below this range, the resist compositionwould become poor in some of the desired properties. The properties ofthe resist composition can be adjusted by properly changing the blendratio of the inventive polymer.

[0111] The other polymer is not limited to one type and a mixture of twoor more other polymers may be added. The use of plural polymers allowsfor easy adjustment of resist properties.

[0112] Dissolution Regulator

[0113] To the resist composition, a dissolution regulator may be added.The dissolution regulator is a compound having on the molecule at leasttwo phenolic hydroxyl groups, in which an average of from 0 to 100 mol %of all the hydrogen atoms on the phenolic hydroxyl groups are replacedwith acid labile groups or a compound having on the molecule at leastone carboxyl group, in which an average of 50 to 100 mol % of all thehydrogen atoms on the carboxyl groups are replaced with acid labilegroups, both the compounds having an average molecular weight within arange of 100 to 1,000, and preferably 150 to 800.

[0114] The degree of substitution of the hydrogen atoms on the phenolichydroxyl groups with acid labile groups is on average at least 0 mol %,and preferably at least 30 mol %, of all the phenolic hydroxyl groups.The upper limit is 100 mol %, and preferably 80 mol %. The degree ofsubstitution of the hydrogen atoms on the carboxyl groups with acidlabile groups is on average at least 50 mol %, and preferably at least70 mol %, of all the carboxyl groups, with the upper limit being 100 mol%.

[0115] Preferable examples of such compounds having two or more phenolichydroxyl groups or compounds having at least one carboxyl group includethose of formulas (D1) to (D14) below.

[0116] In these formulas, R²⁰¹ and R²⁰² are each hydrogen or a straightor branched alkyl or alkenyl of 1 to 8 carbon atoms; R²⁰³ is hydrogen, astraight or branched alkyl or alkenyl of 1 to 8 carbon atoms, or—(R²⁰⁷)_(h)—COOH; R²⁰⁴ is —(CH₂)_(i)— (where i=2 to 10), an arylene of 6to 10 carbon atoms, carbonyl, sulfonyl, an oxygen atom, or a sulfuratom; R²⁰⁵ is an alkylene of 1 to 10 carbon atoms, an arylene of 6 to 10carbon atoms, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom; R²⁰⁶is hydrogen, a straight or branched alkyl or alkenyl of 1 to 8 carbonatoms, or a hydroxyl-substituted phenyl or naphthyl; R²⁰⁷ is a straightor branched alkylene of 1 to 10 carbon atoms; R²⁰⁸ is hydrogen orhydroxyl; the letter j is an integer from 0 to 5; u and h are each 0 or1; s, t, s′, t′, s″, and t″ are each numbers which satisfy s+t=8,s′+t′=5, and s″+t″=4, and are such that each phenyl skeleton has atleast one hydroxyl group; and α is a number such that the compounds offormula (D8) or (D9) have a molecular weight of from 100 to 1,000.

[0117] In the above formulas, suitable examples of R²⁰¹ and R²⁰² includehydrogen, methyl, ethyl, butyl, propyl, ethynyl, and cyclohexyl;suitable examples of R²⁰³ include the same groups as for R²⁰¹ and R²⁰²,as well as —COOH and —CH₂COOH; suitable examples of R²⁰⁴ includeethylene, phenylene, carbonyl, sulfonyl, oxygen, and sulfur; suitableexamples of R²⁰⁵ include methylene as well as the same groups as forR²⁰⁴; and suitable examples of R²⁰⁶ include hydrogen, methyl, ethyl,butyl, propyl, ethynyl, cyclohexyl, and hydroxyl-substituted phenyl ornaphthyl.

[0118] Exemplary acid labile groups on the dissolution regulator includegroups of the following general formulae (L1) to (L4), tertiary alkylgroups of 4 to 20 carbon atoms, trialkylsilyl groups in which each ofthe alkyls has 1 to 6 carbon atoms, and oxoalkyl groups of 4 to 20carbon atoms.

[0119] In these formulas, R^(L01) and R^(L02) are each hydrogen or astraight, branched or cyclic alkyl having 1 to 18 carbon atoms; andR^(L03) is a monovalent hydrocarbon group of 1 to 18 carbon atoms whichmay contain a heteroatom (e.g., oxygen). A pair of R^(L01) and R^(L02),a pair of R^(L01) and R^(L03), or a pair of R^(L02) and R^(L03) maytogether form a ring, with the proviso that R^(L01), R^(L02), andR^(L03) are each a straight or branched alkylene of 1 to 18 carbon atomswhen they form a ring. R^(L04) is a tertiary alkyl group of 4 to 20carbon atoms, a trialkysilyl group in which each of the alkyls has 1 to6 carbon atoms, an oxoalkyl group of 4 to 20 carbon atoms, or a group ofthe formula (L1). R^(L05) is a straight, branched or cyclic alkyl groupof 1 to 8 carbon atoms or a substituted or unsubstituted aryl group of 6to 20 carbon atoms. R^(L06) is a straight, branched or cyclic alkylgroup of 1 to 8 carbon atoms or a substituted or unsubstituted arylgroup of 6 to 20 carbon atoms. R^(L07) to R^(L16) independentlyrepresent hydrogen or monovalent hydrocarbon groups of 1 to 15 carbonatoms which may contain a hetero atom. Alternatively, R^(L07) toR^(L16), taken together, may form a ring. Each of R^(L07) to R^(L16)represents a divalent C₁-C₁₅ hydrocarbon group which may contain ahetero atom, when they form a ring. Two of R^(L07) to R^(L16) which areattached to adjoining carbon atoms may bond together directly to form adouble bond. Letter y is an integer of 0 to 6. Letter m is equal to 0 or1, n is equal to 0, 1, 2 or 3, and 2m+n is equal to 2 or 3.

[0120] The dissolution regulator may be formulated in an amount of 0 to50 parts, preferably 5 to 50 parts, and more preferably 10 to 30 parts,per 100 parts of the base resin, and may be used singly or as a mixtureof two or more thereof. Less than 5 parts of the dissolution regulatormay fail to yield an improved resolution, whereas the use of more than50 parts would lead to slimming of the patterned film, and thus adecline in resolution.

[0121] The dissolution regulator can be synthesized by introducing acidlabile groups into a compound having phenolic hydroxyl or carboxylgroups in accordance with an organic chemical formulation.

[0122] Basic Compound

[0123] In the resist composition of the invention, a basic compound maybe blended. A suitable basic compound used herein is a compound capableof suppressing the rate of diffusion when the acid generated by thephotoacid generator diffuses within the resist film. The inclusion ofthis type of basic compound holds down the rate of acid diffusion withinthe resist film, resulting in better resolution. In addition, itsuppresses changes in sensitivity following exposure, thus reducingsubstrate and environment dependence, as well as improving the exposurelatitude and the pattern profile.

[0124] Examples of basic compounds include primary, secondary, andtertiary aliphatic amines, mixed amines, aromatic amines, heterocyclicamines, carboxyl group-bearing nitrogenous compounds, sulfonylgroup-bearing nitrogenous compounds, hydroxyl group-bearing nitrogenouscompounds, hydroxyphenyl group-bearing nitrogenous compounds, alcoholicnitrogenous compounds, amide derivatives, and imide derivatives.

[0125] Examples of suitable primary aliphatic amines include ammonia,methylamine, ethylamine, n-propylamine, isopropyl-amine, n-butylamine,iso-butylamine, sec-butylamine, tert-butylamine, pentylamine,tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine,heptylamine, octylamine, nonylamine, decylamine, dodecylamine,cetylamine, methylenediamine, ethylenediamine, andtetraethylenepentamine. Examples of suitable secondary aliphatic aminesinclude dimethylamine, diethylamine, di-n-propylamine,di-iso-propylamine, di-n-butylamine, di-iso-butylamine,di-sec-butylamine, dipentylamine, dicyclopentylamine, dihexylamine,dicyclohexylamine, diheptylamine, dioctylamine, dinonylamine,didecylamine, didodecylamine, dicetylamine,N,N-dimethylmethylenediamine, N,N-dimethylethylenediamine, andN,N-dimethyltetraethylenepentamine. Examples of suitable tertiaryaliphatic amines include trimethylamine, triethylamine,tri-n-propylamine, tri-iso-propylamine, tri-n-butylamine,tri-iso-butylamine, tri-sec-butylamine, tripentylamine,tricyclopentylamine, trihexylamine, tricyclohexylamine, triheptylamine,trioctylamine, trinonylamine, tridecylamine, tridodecylamine,tricetylamine, N,N,N′,N′-tetramethylmethylenediamine,N,N,N′,N′-tetramethylethylenediamine, andN,N,N′,N′-tetramethyltetraethylenepentamine.

[0126] Examples of suitable mixed amines include dimethylethylamine,methylethylpropylamine, benzylamine, phenethylamine, andbenzyldimethylamine. Examples of suitable aromatic and heterocyclicamines include aniline derivatives (e.g., aniline, N-methylaniline,N-ethylaniline, N-propylaniline, N,N-dimethylaniline, 2-methylaniline,3-methylaniline, 4-methylaniline, ethylaniline, propylaniline,trimethylaniline, 2-nitroaniline, 3-nitroaniline, 4-nitroaniline,2,4-dinitroaniline, 2,6-dinitroaniline, 3,5-dinitroaniline, andN,N-dimethyltoluidine), diphenyl(p-tolyl)amine, methyldiphenylamine,triphenylamine, phenylenediamine, naphthylamine, diaminonaphthalene,pyrrole derivatives (e.g., pyrrole, 2H-pyrrole, 1-methylpyrrole,2,4-dimethylpyrrole, 2,5-dimethylpyrrole, and N-methylpyrrole), oxazolederivatives (e.g., oxazole and isooxazole), thiazole derivatives (e.g.,thiazole and isothiazole), imidazole derivatives (e.g., imidazole,4-methylimidazole, and 4-methyl-2-phenylimidazole), pyrazolederivatives, furazan derivatives, pyrroline derivatives (e.g., pyrrolineand 2-methyl-1-pyrroline), pyrrolidine derivatives (e.g., pyrrolidine,N-methylpyrrolidine, pyrrolidinone, and N-methylpyrrolidone),imidazoline derivatives, imidazolidine derivatives, pyridine derivatives(e.g., pyridine, methylpyridine, ethylpyridine, propylpyridine,butylpyridine, 4-(1-butylpentyl)pyridine, dimethylpyridine,trimethylpyridine, triethylpyridine, phenylpyridine,3-methyl-2-phenylpyridine, 4-tert-butylpyridine, diphenylpyridine,benzylpyridine, methoxypyridine, butoxypyridine, dimethoxypyridine,1-methyl-2-pyridine, 4-pyrrolidinopyridine, 1-methyl-4-phenylpyridine,2-(1-ethylpropyl)pyridine, aminopyridine, and dimethylaminopyridine),pyridazine derivatives, pyrimidine derivatives, pyrazine derivatives,pyrazoline derivatives, pyrazolidine derivatives, piperidinederivatives, piperazine derivatives, morpholine derivatives, indolederivatives, isoindole derivatives, 1H-indazole derivatives, indolinederivatives, quinoline derivatives (e.g., quinoline and3-quinolinecarbonitrile), isoquinoline derivatives, cinnolinederivatives, quinazoline derivatives, quinoxaline derivatives,phthalazine derivatives, purine derivatives, pteridine derivatives,carbazole derivatives, phenanthridine derivatives, acridine derivatives,phenazine derivatives, 1,10-phenanthroline derivatives, adeninederivatives, adenosine derivatives, guanine derivatives, guanosinederivatives, uracil derivatives, and uridine derivatives.

[0127] Examples of suitable carboxyl group-bearing nitrogenous compoundsinclude aminobenzoic acid, indolecarboxylic acid, and amino acidderivatives (e.g. nicotinic acid, alanine, alginine, aspartic acid,glutamic acid, glycine, histidine, isoleucine, glycylleucine, leucine,methionine, phenylalanine, threonine, lysine,3-aminopyrazine-2-carboxylic acid, and methoxyalanine). Examples ofsuitable sulfonyl group-bearing nitrogenous compounds include3-pyridinesulfonic acid and pyridinium p-toluenesulfonate. Examples ofsuitable hydroxyl group-bearing nitrogenous compounds, hydroxyphenylgroup-bearing nitrogenous compounds, and alcoholic nitrogenous compoundsinclude 2-hydroxypyridine, aminocresol, 2,4-quinolinediol,3-indolemethanol hydrate, monoethanolamine, diethanolamine,triethanolamine, N-ethyldiethanolamine, N,N-diethylethanolamine,triisopropanolamine, 2,2′-iminodiethanol, 2-aminoethanol,3-amino-1-propanol, 4-amino-1-butanol, 4-(2-hydroxyethyl)morpholine,2-(2-hydroxyethyl)pyridine, 1-(2-hydroxyethyl)piperazine,1-[2-(2-hydroxyethoxy)ethyl]piperazine, piperidine ethanol,1-(2-hydroxyethyl)pyrrolidine, 1-(2-hydroxyethyl)-2-pyrrolidinone,3-piperidino-1,2-propanediol, 3-pyrrolidino-1,2-propanediol,8-hydroxyjulolidine, 3-quinuclidinol, 3-tropanol, 1-methyl-2-pyrrolidineethanol, 1-aziridine ethanol, N-(2-hydroxyethyl)phthalimide, andN-(2-hydroxyethyl)isonicotinamide. Examples of suitable amidederivatives include formamide, N-methylformamide, N,N-dimethylformamide,acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide, andbenzamide. Suitable imide derivatives include phthalimide, succinimide,and maleimide.

[0128] In addition, basic compounds of the following general formula(B1) may also be included alone or in admixture.

N(X)_(n)(Y)_(3-n)  B1

[0129] In the formula, n is equal to 1, 2 or 3; Y is independentlyhydrogen or a straight, branched or cyclic alkyl group of 1 to 20 carbonatoms which may contain a hydroxyl group or ether; and X isindependently selected from groups of the following general formulas(X1) to (X3), and two or three X's may bond together to form a ring.

[0130] In the formulas, R³⁰⁰, R³⁰² and R³⁰⁵ are independently straightor branched alkylene groups of 1 to 4 carbon atoms; R³⁰¹ and R³⁰⁴ areindependently hydrogen, straight, branched or cyclic alkyl groups of 1to 20 carbon atoms, which may contain at least one hydroxyl group,ether, ester or lactone ring; and R³⁰³ is a single bond or a straight orbranched alkylene group of 1 to 4 carbon atoms.

[0131] Illustrative examples of the compounds of formula (B1) includetris(2-methoxymethoxyethyl)amine, tris{2-(methoxyethoxy)ethyl}amine,tris{2-(2-methoxyethoxymethoxy)ethyl}amine,tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine,tris{2-(1-ethoxypropoxy)ethyl}amine,tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine,4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo-[8.8.8]hexacosane,4,7,13,18-tetraoxa-1,10-diazabicyclo-[8.5.5]eicosane,1,4,10,13-tetraoxa-7,16-diazabicyclooctadecane, 1-aza-12-crown-4,1-aza-15-crown-5, 1-aza-18-crown-6, tris(2-formyloxyethyl)amine,tris(2-acetoxyethyl)amine, tris(2-propionyloxyethyl)amine,tris(2-butyryloxyethyl)amine, tris(2-isobutyryloxyethyl)amine,tris(2-valeryloxyethyl)amine, tris(2-pivaloyloxyethyl)amine,N,N-bis(2-acetoxyethyl)-2-(acetoxyacetoxy)ethylamine,tris(2-methoxycarbonyloxyethyl)amine,tris(2-tert-butoxycarbonyloxyethyl)amine,tris[2-(2-oxopropoxy)ethyl]amine,tris[2-(methoxycarbonylmethyl)oxyethyl]amine,tris[2-(tert-butoxycarbonylmethyloxy)ethyl]amine,tris[2-(cyclohexyloxycarbonylmethyloxy)ethyl]amine,tris(2-methoxycarbonylethyl)amine, tris(2-ethoxycarbonylethyl)amine,N,N-bis(2-hydroxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-hydroxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-acetoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]ethylamine,N,N-bis(2-acetoxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine,N,N-bis(2-acetoxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine,N,N-bis(2-hydroxyethyl)-2-(4-hydroxybutoxycarbonyl)ethylamine,N,N-bis(2-formyloxyethyl)-2-(4-formyloxybutoxycarbonyl)ethylamine,N,N-bis(2-formyloxyethyl)-2-(2-formyloxyethoxycarbonyl)ethylamine,N,N-bis(2-methoxyethyl)-2-(methoxycarbonyl)ethylamine,N-(2-hydroxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-hydroxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(3-hydroxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(3-acetoxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-methoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(2-methoxyethoxycarbonyl)ethyl]amine,N-methyl-bis(2-acetoxyethyl)amine, N-ethyl-bis(2-acetoxyethyl)amine,N-methyl-bis(2-pivaloyloxyethyl)amine,N-ethyl-bis[2-(methoxycarbonyloxy)ethyl]amine,N-ethyl-bis[2-(tert-butoxycarbonyloxy)ethyl]amine,tris(methoxycarbonylmethyl)amine, tris(ethoxycarbonylmethyl)amine,N-butyl-bis(methoxycarbonylmethyl)amine,N-hexyl-bis(methoxycarbonylmethyl)amine, andβ-(diethylamino)-δ-valerolactone.

[0132] The basic compound is preferably formulated in an amount of 0.001to 10 parts, and especially 0.01 to 1 part, per part of the photoacidgenerator. Less than 0.001 part of the basic compound fails to achievethe desired effects thereof, while the use of more than 10 parts wouldresult in too low a sensitivity and resolution.

[0133] Other Components

[0134] In the resist composition, a compound bearing a ≡C—COOH group ina molecule may be blended. Exemplary, non-limiting compounds bearing a≡C—COOH group include one or more compounds selected from Groups I andII below. Including this compound improves the PED stability of theresist and ameliorates edge roughness on nitride film substrates.

[0135] Group I:

[0136] Compounds in which some or all of the hydrogen atoms on thephenolic hydroxyl groups of the compounds of general formulas (A1) to(A10) below have been replaced with —R⁴⁰¹—COOH (wherein R⁴⁰¹ is astraight or branched alkylene of 1 to 10 carbon atoms), and in which themolar ratio C/(C+D) of phenolic hydroxyl groups (C) to ≡C—COOH groups(D) in the molecule is from 0.1 to 1.0.

[0137] In these formulas, R⁴⁰⁸ is hydrogen or methyl; R⁴⁰² and R⁴⁰³ areeach hydrogen or a straight or branched alkyl or alkenyl of 1 to 8carbon atoms; R⁴⁰⁴ is hydrogen, a straight or branched alkyl or alkenylof 1 to 8 carbon atoms, or a —(R⁴⁰⁹)_(h)—COOR′ group (R′ being hydrogenor —R⁴⁰⁹—COOH); R⁴⁰⁵ is —(CH₂)_(i)— (wherein i is 2 to 10), an aryleneof 6 to 10 carbon atoms, carbonyl, sulfonyl, an oxygen atom, or a sulfuratom; R⁴⁰⁶ is an alkylene of 1 to 10 carbon atoms, an arylene of 6 to 10carbon atoms, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom; R⁴⁰⁷is hydrogen, a straight or branched alkyl or alkenyl of 1 to 8 carbonatoms, or a hydroxyl-substituted phenyl or naphthyl; R⁴⁰⁹ is a straightor branched alkylene of 1 to 10 carbon atoms; R⁴¹⁰ is hydrogen, astraight or branched alkyl or alkenyl of 1 to 8 carbon atoms, or a—R⁴¹¹— COOH group; R⁴¹¹ is a straight or branched alkylene of 1 to 10carbon atoms; the letter j is an integer from 0 to 5; u and h are each 0or 1; s1, t1, s2, t2, s3, t3, s4, and t4 are each numbers which satisfys1+t1=8, s2+t2=5, s3+t3=4, and s4+t4=6, and are such that each phenylskeleton has at least one hydroxyl group; κ is a number such that thecompound of formula (A6) may have a weight average molecular weight of1,000 to 5,000; and λ is a number such that the compound of formula (A7)may have a weight average molecular weight of 1,000 to 10,000.

[0138] Group II:

[0139] Compounds of general formulas (A11) to (A15) below.

[0140] In these formulas, R⁴⁰², R⁴⁰³, and R⁴¹¹ are as defined above;R⁴¹² is hydrogen or hydroxyl; s5 and t5 are numbers which satisfy s5≧0,t5≧0, and s5+t5=5; and h′ is equal to 0 or 1.

[0141] Illustrative, non-limiting examples of the compound bearing a≡—C—COOH group include compounds of the general formulas AI-1 to AI-14and AII-1 to AII-10 below.

[0142] In the above formulas, R″ is hydrogen or a CH₂COOH group suchthat the CH₂COOH group accounts for 10 to 100 mol % of R″ in eachcompound, α and κ are as defined above.

[0143] The compound bearing a ≡C—COOH group within the molecule may beused singly or as combinations of two or more thereof.

[0144] The compound bearing a ≡C—COOH group within the molecule is addedin an amount ranging from 0 to 5 parts, preferably 0.1 to 5 parts, morepreferably 0.1 to 3 parts, further preferably 0.1 to 2 parts, per 100parts of the base resin. More than 5 parts of the compound can reducethe resolution of the resist composition.

[0145] The resist composition of the invention may additionally includean acetylene alcohol derivative for the purpose of enhancing the shelfstability. Preferred acetylene alcohol derivatives are those having thegeneral formula (S1) or (S2) below.

[0146] In the formulas, R⁵⁰¹, R⁵⁰², R⁵⁰³, R⁵⁰⁴, and R⁵⁰⁵ are eachhydrogen or a straight, branched, or cyclic alkyl of 1 to 8 carbonatoms; and X and Y are each 0 or a positive number, satisfying 0≦X≦30,0≦Y≦30, and 0≦X+Y≦40.

[0147] Preferable examples of the acetylene alcohol derivative includeSurfynol 61, Surfynol 82, Surfynol 104, Surfynol 104E, Surfynol 104H,Surfynol 104A, Surfynol TG, Surfynol PC, Surfynol 440, Surfynol 465, andSurfynol 485 from Air Products and Chemicals Inc., and Surfynol E1004from Nisshin Chemical Industry K.K.

[0148] The acetylene alcohol derivative is preferably added in an amountof 0.01 to 2% by weight, and more preferably 0.02 to 1% by weight, per100% by weight of the resist composition. Less than 0.01% by weightwould be ineffective for improving coating characteristics and shelfstability, whereas more than 2% by weight would result in a resisthaving a low resolution.

[0149] The resist composition of the invention may include, as anoptional ingredient, a surfactant which is commonly used for improvingthe coating characteristics. Optional ingredients may be added inconventional amounts so long as this does not compromise the objects ofthe invention.

[0150] Nonionic surfactants are preferred, examples of which includeperfluoroalkylpolyoxyethylene ethanols, fluorinated alkyl esters,perfluoroalkylamine oxides, perfluoroalkyl EO-addition products, andfluorinated organosiloxane compounds. Useful surfactants arecommercially available under the trade names Florade FC-430 and FC-431from Sumitomo 3M K.K., Surflon S-141 and S-145 from Asahi Glass K.K.,Unidine DS-401, DS-403 and DS-451 from Daikin Industry K.K., MegafaceF-8151 from Dai-Nippon Ink & Chemicals K.K., and X-70-092 and X-70-093from Shin-Etsu Chemical Co., Ltd. Preferred surfactants are FloradeFC-430 from Sumitomo 3M K.K. and X-70-093 from Shin-Etsu Chemical Co.,Ltd.

[0151] Pattern formation using the resist composition of the inventionmay be carried out by a known lithographic technique. For example, theresist composition is applied onto a substrate such as a silicon waferby spin coating or the like to form a resist film having a thickness of0.3 to 2.0 μm, which is then pre-baked on a hot plate at 60 to 150° C.for 1 to 10 minutes, and preferably at 80 to 130° C. for 1 to 5 minutes.A patterning mask having the desired pattern is then placed over theresist film, and the film exposed through the mask to an electron beamor to high-energy radiation such as deep-UV rays, excimer laser light,or x-rays in a dose of about 1 to 200 mJ/cm², and preferably about 10 to100 mJ/cm², then post-exposure baked (PEB) on a hot plate at 60 to 150°C. for 1 to 5 minutes, and preferably at 80 to 130° C. for 1 to 3minutes. Finally, development is carried out using as the developer anaqueous alkali solution, such as a 0.1 to 5% (preferably 2 to 3%)aqueous solution of tetramethylammonium hydroxide (TMAH), this beingdone by a conventional method such as dipping, puddling, or spraying fora period of 0.1 to 3 minutes, and preferably 0.5 to 2 minutes. Thesesteps result in the formation of the desired pattern on the substrate.Of the various types of high-energy radiation that may be used, theresist composition of the invention is best suited to fine patternformation with, in particular, deep-UV rays having a wavelength of 248to 193 nm, excimer laser light, x-rays, or an electron beam. The desiredpattern may not be obtainable outside the upper and lower limits of theabove range.

[0152] The resist composition comprising the polymer as a base resinlends itself to micropatterning with electron beams or deep-UV rayssince it is sensitive to high-energy radiation and has excellentsensitivity, resolution, and etching resistance. Especially because ofthe minimized absorption at the exposure wavelength of an ArF or KrFexcimer laser, a finely defined pattern having sidewalls perpendicularto the substrate can easily be formed.

EXAMPLE

[0153] Synthesis Examples and Examples are given below by way ofillustration and not by way of limitation.

Synthesis Examples

[0154] Polymers were synthesized according to the following formulation.

Synthesis Example 1 Synthesis of Polymer 1

[0155] In 1 liter of tetrahydrofuran were dissolved 80.0 g of1-ethylcyclopentyl 3-(bicyclo[2.2.1]-2-hepten-5-yl)-3-acetoxypropionate(which had been synthesized by reactingbicyclo[2.2.1]-5-heptene-2-carbaldehyde and 1-ethylcyclopentyl acetatein the presence of lithium hexamethyldisilazide and acetylating theresulting hydroxyl groups) and 24.5 g of maleic anhydride. To thesolution, 1.8 g of 2,2′-azobisisobutyronitrile was added. Afteragitation was continued for 15 hours at 60° C., the reaction solutionwas concentrated in vacuum. The residue was dissolved in 400 ml oftetrahydrofuran, which was, in turn, added dropwise to 10 liters ofn-hexane. The resulting solids were collected by filtration, washed with10 liters of n-hexane, and dried in vacuum at 40° C. for 6 hours,obtaining 59.5 g of a polymer, designated Polymer 1. The yield was56.9%.

[0156] The polymer was measured for transmittance at a wavelength of 193nm, finding a transmittance of 78.0% at a film thickness of 500 nm.

Synthesis Examples 2 to 12 Synthesis of Polymers 2 to 12

[0157] Polymers 2 to 12 were synthesized by the same procedure as aboveor a well-known procedure.

Example I

[0158] Resist compositions were formulated using inventive polymers andexamined for resolution upon KrF excimer laser exposure.

Examples I-1 to I-22 Evaluation of Resist Resolution

[0159] Resist compositions were prepared by using Polymers 1 to 12 asthe base resin, and mixing the polymer, a photoacid generator(designated as PAG 1 and 2), a dissolution regulator (designated as DRR1 to 4), a basic compound, and a compound having a ≡C—COOH group in themolecule (ACC 1 and 2) in a solvent in accordance with the formulationshown in Table 1. These compositions were each filtered through a Teflonfilter (pore diameter 0.2 μm), thereby giving resist solutions.

[0160] The solvents and basic compounds used are as follows. It is notedthat the solvents contained 0.01% by weight of surfactant Florade FC-430(Sumitomo 3M).

[0161] PGMEA: propylene glycol methyl ether acetate

[0162] TBA: tributylamine

[0163] TEA: triethanolamine

[0164] TMMEA: trismethoxymethoxyethylamine

[0165] TMEMEA: trismethoxyethoxymethoxyethylamine

[0166] These resist solutions were spin-coated onto silicon wafers, thenbaked on a hot plate at 110° C. for 90 seconds to give resist filmshaving a thickness of 0.5 μm. The resist films were exposed using an KrFexcimer laser stepper (Nikon Corporation; NA 0.5), then baked (PEB) at110° C. for 90 seconds, and developed with a solution of 2.38% TMAH inwater, thereby giving positive patterns.

[0167] The resulting resist patterns were evaluated as described below.First, the sensitivity (Eth, mJ/cm²) was determined. Next, the optimumdose (Eop, mJ/cm²) was defined as the dose which provides a 1:1resolution at the top and bottom of a 0.30 μm line-and-space pattern,and the resolution of the resist under evaluation was defined as theminimum line width (μm) of the lines and spaces that separated at thisdose. The shape of the resolved resist pattern was examined under ascanning electron microscope.

[0168] The composition and test results of the resist materials areshown in Table 1. TABLE 1 Photoacid Dissolution Basic Optimum Base resingenerator regulator compound Solvent dose Resolution Example (pbw) (pbw)(pbw) (pbw) (pbw) (mJ/cm²) (μm) Shape I-1  Polymer 1 PAG 1 TBA PGMEA23.5 0.22 rectangular (80) (1) (0.078) (480) I-2  Polymer 2 PAG 1 TBAPGMEA 20.0 0.22 rectangular (80) (1) (0.078) (480) I-3  Polymer 3 PAG 1TEA PGMEA 21.5 0.22 rectangular (80) (1) (0.078) (480) I-4  Polymer 4PAG 1 TBA PGMEA 24.0 0.22 rectangular (80) (1) (0.078) (480) I-5 Polymer 5 PAG 1 TBA PGMEA 25.0 0.24 rectangular (80) (1) (0.078) (480)I-6  Polymer 6 PAG 1 TBA PGMEA 24.0 0.22 rectangular (80) (1) (0.078)(480) I-7  Polymer 7 PAG 1 TBA PGMEA 21.0 0.22 rectangular (80) (1)(0.078) (480) I-8  Polymer 8 PAG 1 TBA PGMEA 20.0 0.22 rectangular (80)(1) (0.078) (480) I-9  Polymer 9 PAG 1 TBA PGMEA 20.0 0.22 rectangular(80) (1) (0.078) (480) I-10  Polymer 10 PAG 1 TBA PGMEA 20.5 0.22rectangular (80) (1) (0.078) (480) I-11  Polymer 11 PAG 1 TBA PGMEA 21.00.22 rectangular (80) (1) (0.078) (480) I-12  Polymer 12 PAG 1 TBA PGMEA24.5 0.22 rectangular (80) (1) (0.078) (480) I-13 Polymer 2 PAG 2 TBAPGMEA 21.0 0.22 rectangular (80) (1) (0.078) (480) I-14 Polymer 2 PAG 2TEA PGMEA 22.5 0.20 rectangular (80) (1) (0.063) (480) I-15 Polymer 2PAG 2 TMMEA PGMEA 23.0 0.20 rectangular (80) (1) (0.118) (480) I-16Polymer 2 PAG 2 TMEMEA PGMEA 23.0 0.20 rectangular (80) (1) (0.173)(480) I-17 Polymer 3 PAG 2 DRR 1 TMMEA PGMEA 21.5 0.22 rectangular (70)(1) (10) (0.118) (480) I-18 Polymer 3 PAG 2 DRR 2 TMMEA PGMEA 20.5 0.20rectangular (70) (1) (10) (0.118) (480) I-19 Polymer 3 PAG 2 DRR 3 TMMEAPGMEA 24.0 0.22 rectangular (70) (1) (10) (0.118) (480) I-20 Polymer 3PAG 2 DRR 4 TMMEA PGMEA 22.0 0.20 rectangular (70) (1) (10) (0.118)(480) I-21 Polymer 3 PAG 2 ACC 1 TMMEA PGMEA 23.0 0.20 rectangular (80)(1) (4) (0.118) (480) I-22 Polymer 3 PAG 2 ACC 2 TMMEA PGMEA 24.0 0.20rectangular (80) (1) (4) (0.118) (480)

[0169] It is seen from Table 1 that the resist compositions within thescope of the invention have a high sensitivity and resolution upon KrFexcimer laser exposure.

Example II

[0170] Resist compositions were formulated using inventive polymers andexamined for resolution upon ArF excimer laser exposure.

Examples II-1 to II-2 Evaluation of Resist Resolution

[0171] Resist compositions were prepared as in Example I in accordancewith the formulation shown in Table 2.

[0172] The resulting resist solutions were spin-coated onto siliconwafers, then baked on a hot plate at 110° C. for 90 seconds to giveresist films having a thickness of 0.5 μm. The resist films were exposedusing an ArF excimer laser stepper (Nikon Corporation; NA 0.55), thenbaked (PEB) at 110° C. for 90 seconds, and developed with a solution of2.38% TMAH in water, thereby giving positive patterns.

[0173] The resulting resist patterns were evaluated as described below.First, the sensitivity (Eth, mJ/cm²) was determined. Next, the optimumdose (Eop, mJ/cm²) was defined as the dose which provides a 1:1resolution at the top and bottom of a 0.25 μm line-and-space pattern,and the resolution of the resist under evaluation was defined as theminimum line width (μm) of the lines and spaces that separated at thisdose. The shape of the resolved resist pattern was examined under ascanning electron microscope.

[0174] The composition and test results of the resist materials areshown in Table 2. TABLE 2 Photoacid Dissolution Basic Optimum Base resingenerator regulator compound Solvent dose Resolution Example (pbw) (pbw)(pbw) (pbw) (pbw) (mJ/cm²) (μm) Shape II-1 Polymer 2 PAG2 TEA PGMEA 16.00.15 rectangular (80) (1) (0.063) (480) II-2 Polymer 3 PAG2 DRR4 TMMEAPGMEA 15.0 0.15 rectangular (70) (1) (10) (0.118) (480)

[0175] It is seen from Table 2 that the resist compositions within thescope of the invention have a high sensitivity and resolution upon ArFexcimer laser exposure.

[0176] Japanese Patent Application No. 2000-129042 is incorporatedherein by reference.

[0177] Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

1. A polymer comprising units of the following general formula (1) andunits of the following general formula (2) and having a weight averagemolecular weight of 1,000 to 500,000,

wherein R¹ is hydrogen, methyl or CH₂CO₂R³, R² is hydrogen, methyl orCO₂R³, R³ is a straight, branched or cyclic alkyl group of 1 to 15carbon atoms, R⁴ is a halogen atom or an acyloxy, alkoxycarbonyloxy oralkylsulfonyloxy group of 1 to 15 carbon atoms in which some or all ofthe hydrogen atoms on the constituent carbon atoms may be substitutedwith halogen atoms, R⁵ is hydrogen or a straight, branched or cyclicalkyl group of 1 to 10 carbon atoms, R⁶ is an acid labile group, Z is asingle bond or a divalent straight, branched or cyclic hydrocarbon groupof 1 to 10 carbon atoms, k is 0 or 1, and W is —O— or —(NR)— wherein Ris hydrogen or a straight, branched or cyclic alkyl group of 1 to 15carbon atoms.
 2. The polymer of claim 1 wherein the units of formula (1)are units of the following general formula (3) or (4):

wherein R¹ to R⁵, Z, and k are as defined above, R⁷ to R¹⁰ areindependently selected from straight, branched or cyclic alkyl groups of1 to 8 carbon atoms and substituted or unsubstituted aryl groups of 6 to20 carbon atoms, and Y is a divalent hydrocarbon group of 4 to 15 carbonatoms which may contain a hetero atom and which forms a ring with thecarbon atom to which it is connected at opposite ends.
 3. The polymer ofclaim 1 or 2 further comprising units of at least one of the followingformulas (5) to (8):

wherein R¹, R² and k are as defined above, at least one of R¹¹ to R¹⁴ isa carboxyl or hydroxyl-containing monovalent hydrocarbon group of 1 to15 carbon atoms, and the remainders are independently hydrogen or astraight, branched or cyclic alkyl group of 1 to 15 carbon atoms, or R¹¹to R¹⁴, taken together, may form a ring, and when they form a ring, atleast one of R¹¹ to R¹⁴ is a carboxyl or hydroxyl-containing divalenthydrocarbon group of 1 to 15 carbon atoms, and the remainders areindependently a single bond or a straight, branched or cyclic alkylenegroup of 1 to 15 carbon atoms, at least one of R¹⁵ to R¹⁸ is amonovalent hydrocarbon group of 2 to 15 carbon atoms containing a —CO₂—partial structure, and the remainders are independently hydrogen or astraight, branched or cyclic alkyl group of 1 to 15 carbon atoms, or R⁵to R¹⁸, taken together, may form a ring, and when they form a ring, atleast one of R¹⁵ to R¹⁸ is a divalent hydrocarbon group of 1 to 15carbon atoms containing a —CO₂— partial structure, and the remaindersare independently a single bond or a straight, branched or cyclicalkylene group of 1 to 15 carbon atoms, R¹⁹ is a polycyclic hydrocarbongroup of 7 to 15 carbon atoms or an alkyl group containing such apolycyclic hydrocarbon group, R²⁰ is an acid labile group, and X is—CH₂— or —O—.
 4. A resist composition comprising the polymer of any oneof claims 1 to 3 .
 5. A process for forming a resist pattern comprisingthe steps of: applying the resist composition of claim 4 onto asubstrate to form a coating, heat treating the coating and then exposingit to high-energy radiation or electron beams through a photo mask, andoptionally heat treating the exposed coating and developing it with adeveloper.